For a joint shaft of a robot, which is rotated by being driven by a motor, the correspondence relationship between the angle of the joint shaft and a sensor signal that is output from a sensor in accordance with the driving amount of the motor is defined. When the motor on the joint shaft, a reduction gear connected to the motor, or the like is reinstalled or replaced, there are cases where the defined correspondence relationship changes. There are known technologies for performing calibration so as to match the correspondence relationship after the change with the correspondence relationship before the change and then using the correspondence relationship defined before the change instead of newly defining the correspondence relationship after the change in such cases (e.g., see Japanese Unexamined Patent Application, Publication No. 2011-251365).
With the technology disclosed in Japanese Unexamined Patent Application, Publication No. 2011-251365, images of two marks individually provided on two members whose amount of relative movement via a joint shaft changes are captured by a camera before and after reinstallation of a motor or the like, and the correspondence relationship after the reinstallation is calibrated by using the positional relationship between the marks in the two acquired images.